The field of the invention relates to methods for treating or preventing macular degeneration. In particular, the invention relates to compositions and methods that are useful for preventing the formation of drusen associated with macular degeneration, such as macular drusen. The compositions and methods also are useful for preventing an increase in the size or amount of existing drusen, or for causing a decrease in the size or amount of existing drusen. The compositions and methods also are useful for preventing the appearance of new drusen.
Macular degeneration is a medical condition predominantly found in elderly adults in which the center of the retina of the eye, otherwise known as the “macula” area of the retina, exhibits thinning, atrophy, and sometimes new blood vessel formation. Macular degeneration can result in the loss of central vision, including the ability to see fine details, to read, or even to recognize faces. According to the American Academy of Ophthalmology, macular degeneration is the leading cause of central vision loss in the United States for those over the age of fifty years. Although macular degeneration sometimes may affect younger individuals, the term generally refers to “age-related” macular degeneration (i.e., “AMD” or “ARMD”).
Early stages of AMD are characterized by development of yellow deposits in the macula called drusen. These deposits form in the macula between the retinal pigment epithelium and the underlying choroid. At this early stage (referred to as the maculopathy stage), most patients still have good vision. However, patients with macular drusen can go on to develop advanced AMD. The risk for developing advanced AMD is considerably higher when the drusen are large and numerous or when the drusen are associated with a disturbance in the pigmented cell layer tinder the macula.
Advanced AMD has two forms referred to as the “dry” and “Wet” forms. The dry form of advanced AMD is characterized by central geographic atrophy, which causes vision loss through the loss of photoreceptors in the central part of the eye (i.e., rods and cones). While no treatment is available for the dry form, the National Eye Institute has suggested that vitamin supplements with high doses of antioxidants may slow the progression of dry macular degeneration and in some patients, improve visual acuity.
The wet form of advanced AMD, otherwise referred to as “neovascular” or “exudative” AMD, causes vision loss due to abnormal blood vessel growth in the choriocapillaries, through a retinal layer referred to as “Bruch's membrane.” The wet form of AMD ultimately leads to blood and protein leakage below the macula. This bleeding, leaking, and scarring below the macula eventually cause irreversible damage to the photoreceptors and rapid vision loss if left untreated. Until recently, no effective treatments were known for wet macular degeneration. However, new drugs that inhibit angiogenesis (i.e., “anti-angiogenic agents”) have been shown to cause regression of the abnormal blood vessels and improvement of vision. In order to be effective, anti-angiogenic agents, such as anti-vascular endothelial growth factor, must be injected directly into the vitreous humor of the eye. Furthermore, anti-angiogenic agents are expensive and must be administered repeatedly several times a year.
Therefore, new compositions and methods for treating or preventing macular degeneration are desirable.